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l'Aj.5    /<w>  Co'NN 

*  S 

0.  E.  S.  Library-  Gop.  2. 

CONNECTICUT  ■ E^ 

AGRICULTURAL  EXPERIMENT  STATION  ^'^ 

NEW     HAVEN,    CONN. 


BULLETIN   140,    SEPTEMBER,    1902. 


ENTOMOLOGICAL    SERIES,    No.    8. 

The  White-fly  or  Plant-house  Aleyrodes. 


CONTENTS. 


Page. 


Officers  and  Staff  of  Station 2 

The  White-fly  or  Plant-house  Aleyrodes 3 

Relationship  to  Other  Insects 4 

How  it  Injures  Plants 5 

Food   Plants 5 

Habits  and  Life  History 7 

Description 8 

Identity  and  Name 10 

Westwood's  Description  of  A,  vaporariorum n 

Bibliography 14 

Remedies  15 

Fumigating 15 

Spraying 15 

Summary 17 


The  Bulletins  of  this  Station  are  mailed  free  to  all  citizens  of 
Connecticut  who  apply  for  them,  and  to  others  as  far  as  the  limited 
editions  permit. 


CONNECTICUT  AGRICULTURAL  EXPERIMENT  STATION. 

OFFICERS    ^JSTJD    STAFF. 


STATE   BOARD    OF    CONTROL. 

Ex  officio. 
His  Excellency  George  P.  McLean,  President. 

Appointed  by  Connecticut  State  Agricultural  Society: 
B.  W.  Collins,  Meriden. 

Appointed  by  Board  of  Trustees  of  Wesleyan  University: 
Prof.  W.  O.  Atwater,  Middletown. 

Appointed  by  Governor  and  Senate: 
Edwin  Hoyt,  New  Canaan. 
James  H.  Webb,  Hamden. 

Appointed  by  Board   of  Agriculture: 
T.   S.   Gold,  West  Cornwall,    Vice  President. 

Appointed  by  Governing  Board  of  Sheffield  Scientific  School: 
W.  H.  Brewer,  New  Haven,  Secretary. 

Ex  officio. 
E.  H.  Jenkins,  New  Haven,  Director  and  Treasurer. 


STATION    STAFF. 

Chemists. 
E.  H.  Jenkins,  Ph.D.,  Director.  A.  W.  Ogden,  Ph.B. 

A.  L.  Winton,  Ph.B.  I.  F.  Harris,  B.S. 

T.  B.  Osborne,  Ph.D.  M.  Silverman,  Ph.B. 

Botanist. 
G.  P.  Clinton,  S.D. 

Entomologist. 
W.  E.  Britton,  B.S. 

In  charge  of  Forestry  Work. 
Walter  Mulford,  F.E. 

Grass  Gardener. 
James  B.  Olcott,  South  Manchester. 

Stenographers  and  Clerks. 

Miss  V.  E.  Cole. 
Miss  L.  M.  Brautlecht. 

In  charge  of  Buildings  and  Grounds. 
William  Veitch. 

Laboratory  Helpers. 
Hugo  Lange.  William  Pokrob. 

Sampling  Agent. 
V.  L.  Churchill,  New  Haven. 


WHITE-FLY   OR   PLANT-HOUSE   ALEYRODES.  3 

THE  WHITE-FLY   OR   PLANT-HOUSE  ALEYRODES. 

Ale yr odes  vaporariorum  Westw.  ? 

By  W.  E.  Britton,,  State  Entomologist. 

For  eight  years  the  most  serious  insect  pest  affecting  forcing- 
house  tomatoes  at  the  Station  has  been  the  "white-fly," 
"mealy-wing,"  or  plant-house  Aleyrodes.  Were  it  impossible 
to  hold  the  insect  in  check,  the  crop  each  winter  would  be  nearly 
a  total  failure.  Seemingly  the  species  grows  more  and  more 
abundant  each  succeeding  year;  at  least  the  remedies  need  to 
be  applied  with  greater  persistence  than  formerly,  and  in  spite 
of  all  the  spraying  and  fumigating  a  goodly  number  of  indi- 
viduals survive. 

The  attacks  of  the  white-fly  are  by  no  means  confined  to 
the  tomato  plant,  but  other  forcing-house  crops,  especially 
cucumbers  and  lettuce,  are  sometimes  seriously  injured.  There 
is  a  large  number  of  florists'  plants  upon  which  the  insect  is 
known  to  live,  and  several  of  them  are  each  year  much  damaged 
by  its  attacks.  Nor  are  the  depredations  of  this  insect  limited 
to  plants  under  glass ;  on  the  contrary,  it  lives  and  multiplies 
on  the  out-door  plants  of  the  garden  through  the  summer,  fre- 
quently causing  more  or  less  injury.  The  white-fly  has  already 
been  reported  as  injuring  strawberry  plants  in  Kentucky*  and 
New  York,f  and  we  may  expect  similar  accounts  of  it  from  other 
localities. 

In  1901  the  white-fly  was  sent  to  the  Station  from  Bridge- 
port, where  it  was  damaging  aster  and  chrysanthemum  plants. 
In  July,  1902,  specimens  were  received  from  Milford  on  straw- 
berry leaves. 

While  on  a  vacation  last  month  the  writer  observed  that  aster 
plants  growing  in  a  garden  in  Surry,  N.  H.,  were  infested  with 
this  insect. 

The  original  home  of  this  Aleyrodes  is  unknown.  West- 
wood  states  that  it  is  supposed  to  have  been  carried  into  Eng- 
land on  plants  from  Mexico.     It  may  have  been  brought  here 

*  Report  of  Kentucky  Experiment  Station  for  1890,  p.  37. 
t  Bulletin  190,  Cornell  Experiment  Station,  p.  155. 


4  CONNECTICUT    EXPERIMENT    STATION,    BULLETIN    I40. 

either  from  England  or  from  Mexico.  Ouaintance  states*  that 
it  has  been  received  by  the  Entomologist  at  Washington  from 
New  Haven  and  Storrs,  Connecticut ;  West  Grove,  Pa.,  and 
Goshen,  Ind. 

It  also  occurs  in  such  widely  separated  regions  as  Michigan, 
Kentucky,  New  York,  Massachusetts,  New  Hampshire,  Ohio 
and  the  District  of  Columbia,  which  indicates  that  it  is  now  thor- 
oughly distributed  throughout  the  northeastern  portion  of  the 
United  States. 

The  plates  in  this  bulletin  are  from  photographs  made  for  the 
author  by  the  late  Mr.  H.  A.  Doty.  The  text  illustrations  were 
engraved  on  wood  by  Mr.  R.  M.  Sherman  from  the  author's 
drawings. 

Relationship  to  Other  Insects. 

The  Aleyrodidcc,  to  which  the  white-fly  belongs,  are  closely 
related  to  the  Coccidce,  or  scale-insects,  being  perhaps  inter- 
mediate between  them  and  the  plant-lice,  Aphididcc.  They  dif- 
fer from  the  former  in  that  both  sexes  are  winged  and  motile, 
and  from  the  latter  in  being  fastened  to  the  plant  in  the  nymph 
stage.  The  larvae  or  nymphs  hatch  from  eggs  deposited  by  the 
females  on  the  under  surface  of  leaves,  and  closely  resemble 
several  species  of  scale-insects. 

Aleyrodid  insects  are  not  considered  to  be  of  very  great 
economic  importance.  They  are  much  more  abundant  in  the 
tropics  than  in  temperate  regions.  Many  species  occur  on  cul- 
tivated and  wild  plants,  but  are  seldom  abundant  enough  to  be 
a  serious  menace  to  them.  Signoret's  monograph  of  the 
Aleyrodidce,  published  in  1868,  contains  twenty-three  species 
found  in  Europe. f  Ouaintance  lists  forty-two  speciesf  in 
America,  but  A.  citri  Riley  &  Howard,  which  is  a  serious 
pest  of  the  orange  and  lemon  groves  of  the  Southern  States,  and 
this  plant-house  aleyrodes  are  without  doubt  the  two  most 
important  species  from  the  standpoint  of  the  horticulturist. 

*  Bull.  8,  Tech.  Series,  Division  of  Entomology,  U.  S.  Department  of 
Agriculture,  p.  39. 

f  Annales  de  la  Societe  Entomologique  de  France,  1868,  p.  387. 

t  Bull.  8,  Tech.  Series,  Division  of  Entomology,  U.  S.  Dept.  of  Agri- 
culture. 


white-fly;   how  it  injures  plants.  5 

How  it  Injures  Plants. 

The  female  lays  eggs  on  the  under  sides  of  the  leaves.  Soon 
after  the  eggs  hatch  the  young  larvae  or  nymphs  attach  them- 
selves to  the  leaf  and  injure  it  by  sucking  out  the  sap  for  their 
nourishment  throughout  the  period  of  larval  growth.  As  each 
female  deposits  several  eggs,  and  as  only  a  short  time  is  required 
for  the  complete  cycle  of  development,  successive  generations 
finally  cover  the  entire  under  surface  of  the  leaf.  The  tissues 
collapse  from  the  effects  of  this  continuous  pumping  out  of  the 
life- juices  of  the  plant,  and  the  leaf  shrivels  and  falls.  As  new 
leaves  are  formed  at  the  top  of  the  plant  these  in  turn  become 
infested,  and  later  wither  and  die.  If  no  efforts  are  made  to 
destroy  the  pest,  the  entire  plant  may  be  dead  before  the  end  of 
the  season,  or  if  it  be  a  vigorous  grower  like  the  tomato,  may 
have  a  few  green  leaves  at  the  top,  with  a  bare  stem  from  which 
the  leaves  have  withered  and  dropped.  In  the  greenhouses  the 
insects  usually  become  very  abundant  towards  the  end  of  the 
season,  and  the  warm  days  of  spring  seem  to  favor  their  multi- 
plication :  this  occurs  in  our  tomato  house  nearly  every  year  in 
spite  of  a  weekly  spraying  which  kills  all  adults  with  which  the 
material  comes  in  contact.  As  the  season  advances  the  plants 
in  the  garden  become  infested  and  the  species  keeps  multiplying 
out  of  doors  until  cold  weather  approaches,  when  it  again 
appears  in  the  greenhouse,  there  to  pass  the  following  winter. 

Though  most  of  the  feeding  is  done  in  the  nymph  stage,  the 
adult  is  provided  with  mouthparts  well  fitted  for  sucking  and 
probably  injures  plants  to  some  extent.  I  have  often  seen  adults 
resting  on  the  lower  surfaces  of  leaves  with  their  beaks  piercing 
the  tissues.  When  disturbed  they  fly  upward,  and  if  abundant 
they  literally  fill  the  upper  portion  of  the  greenhouse.  A  sweet 
sticky  substance  called  honeydew  is  exuded  by  the  insects,  and 
this  covers  the  fruits  and  lower  leaves  of  the  plants  during  the 
latter  part  of  the  winter.  A  black  fungus  grows  in  the  honey- 
dew,  giving  the  plants  the  appearance  of  having  been  covered 
with  soot. 

Food  Plants. 

Although  in  forcing-houses  the  white-fly  has  been  most  trou- 
blesome on  tomato,  cucumber  and  melon  plants,  and  the  florists 
must  fight  it  persistently  on  Ageratum,  Lantana  and  heliotrope, 


6  CONNECTICUT    EXPERIMENT    STATION,    BULLETIN    I40. 

I  believe  that  it  is  able  to  live  upon  and  may  attack  almost  any 
kind  of  plant  if  the  preferred  ones  are  not  at  hand.  Solanaceous 
plants  (those  belonging  to  the  potato  family)  are  favorites,  and 
tobacco  growing  at  the  Station  in  1901  was  badly  infested. 
Should  this  insect  become  established  in  the  tobacco  fields  of 
Connecticut,  it  would  doubtless  prove  a  very  troublesome  pest. 
The  following  list  contains  only  those  plants  upon  which  I 
have  observed  the  insect  in  its  nymph  stages :  the  adults  have 
been  found  resting  upon  the  leaves  of  a  great  many  other  kinds 
of  plants. 


Abutilon  sp. 

Hibiscus  moscheutos. 

Hibiscus  rosa-sinensis. 

Cucumber. 

Squash. 

Melon. 

Potato. 

Tomato. 

Tobacco. 

Strawberry. 

Japan  plum. 

Currant. 

Lettuce. 

Bean. 

Aster. 

Coreopsis  lanceolata. 

Golden  Glow  (Rudbeckia  laciniata) . 

Zinnia. 

Lantana. 

Verbena. 

Heliotrope. 

Calla  lily. 

Snapdragon. 

Smilax. 

Colens. 

Nasturtium   {Tropceolum). 

Chrysanthemum. 

Ageratum  mexicana. 

Columbine. 

Fuchsia. 


Salvia. 

Monarda. 

Maurandya. 

Grevillea  robusta. 

Tecoma  radicans. 

Erigeron  philadelphicum. 

Geranium. 

Pelargonium. 

Nutmeg  (Schinus  molle). 

Oxalis. 

Campanula  sp.  ? 

Parrot's  Feather    (Myriophyllum 

proserpinacoides) . 
Morning  Glory. 
Cigar  plant  (Cupliea). 
Lavendula  dentata. 
Lilium  superbum. 
Solidago  canadensis.. 
Phytolacca  decandra. 
Lonicera. 
Platycodon. 
Phlox. 
Catalpa. 
Hickory. 

Berberis  Thunbergi. 
Rose. 
Spiraea. 

Rhodotypus  kerrioides. 
Spice  bush. 


Westwood  found  it  on  Tecoma  vehitina,  Gonolobus,  Solatium, 
and  plants  belonging  to  the  Bignonicc  and  Aphelandrce. 


white-fly;    habits  and  life  history.  7 

Habits  and  Life  History. 

The  plant-house  aleyrodes  in  all  its  stages  is  found  on  the 
under  sides  of  the  leaves  and  seldom  anywhere  else  unless  dis- 
turbed. The  eggs  are  laid  on  the  leaves,  perhaps,  when  the 
plant  is  small,  and  as  the  new  leaves  are  formed  these  become  the 
ovipositing  places.  Thus  the  lower  leaves  of  large  and  badly 
infested  plants  are  usually  completely  covered  on  their  under 
surfaces  with  the  empty  skins  from  which  the  adults  have 
emerged.  These  leaves  are  the  first  to  wither  and  drop.  Those 
next  higher  up  on  the  plant  will  show  nymphs  and  pupae;  still 
higher  we  shall  find  younger  and  newly  hatched  nymphs,  while 
on  the  upper  leaves  the  adults  will  be  mating  and  the  females 
laying  eggs.  The  process  of  ovipositing  is  an  interesting  one 
and  was  observed  by  the  writer  a  few  years  ago  in  two  cases  on 
lettuce  plants.  The  female  first  thrust  her  beak  into  the  leaf, 
and  depositing  an  egg,  swung  about  with  her  beak  still  inserted 
and  serving  as  a  pivot,  continuing  to  deposit  eggs  in  a  circle  of 
about  one  millimeter  in  diameter.  One  of  these  circles  con- 
tained six,  while  another  had  nine  eggs.  This  peculiar  egg- 
laying  habit  was  observed  many  years  ago  by  Reaumur  in 
Aleyrodes  chelidonii  as  cited  by  Westwood  in  the  Gardener's 
Chronicle  (1856,  p.  852).  But  our  species  does  not  always  lay 
eggs  in  this  manner,  for  I  have  often  found  eggs  deposited  singly 
and  scattered  over  the  surface  of  the  leaf.  Davis  has  observed 
that  on  hairy  plants  like  the  Ageratum  the  eggs  are  deposited 
singly. 

The  eggs  were  light  green  or  nearly  white  at  first  but  soon 
changed  to  a  dark  color,  and  hatched  in  eleven  days.  The 
newly-hatched  larva  moves  about  for  a  short  time,  then  becomes 
stationary  and  resembles  a  scale  insect.  It  increases  in  size  for 
a  time  and  when  fully  grown  changes  to  a  yellowish  color.  Still 
more  important  changes  are  taking  place  inside.  This  is  called 
the  pupa  stage.  Finally  the  skin  cracks  open  along  the  median 
line  of  the  back,  and  transversely  through  the  caret-shaped  line, 
and  the  fully  developed  insect  appears.  It  is  pure  white,  much 
resembling  a  tiny  moth,  and  it  is  entirely  covered  with  particles 
of  wax.  The  old  pupa  skins  remain  attached  to  the  leaf  for  a 
long  time.  The  adults  fly  about,  mate  and  the  female  soon 
begins  to  lay  eggs.     It  is  not  known  how  long  the  insects  live 


8  CONNECTICUT   EXPERIMENT    STATION,    BULLETIN    I40. 

after  reaching  this  stage.  From  the  laying  of  the  egg  to  the 
time  that  the  adult  comes  forth  requires  a  period  of  about  five 
weeks.     Plate  I.  shows  nymphs  and  adults  on  a  leaf. 

It  is  not  known  whether  the  species  can  survive  the  winter 
out  of  doors  in  this  climate,  but  in  the  cases  coming  under  the 
writer's  observation  it  has  been  carried  through  the  cold  weather 
on  plants  in  greenhouses  or  dwellings. 

Description. 

Egg. — Length,  200/^  to  250^  (.2  to  .25  millimeter).  Thick- 
ness, 90/^  to  loo/*  (.09  to  .1  millimeter)  in  thickest  portion. 
Elongated  ovate  in  shape.  White  or  light  green  when  first  laid 
but  soon  (three  days  according  to  Davis)  changing  to  a  dark 
bluish-black.  The  large  end  is  attached  to  the  under  surface 
of  the  leaf  by  means  of  a  very  short  and  slender  thread-like  stalk 
which  is  difficult  to  make  out.  Smooth  and  shiny  or  covered 
with  minute  granules  of  white  wax.  See  fig.  i,  and  plate  III. 
Eggs  observed  by  the  writer  hatched  in  eleven  days. 


Fig.    1. — Eggs  :   X  36.  Fig.   2. — Newly-hatched  nymph, 

ventral  view:    X  55- 

Newly-hatched  Nymph.  —  Length,  about  252/*  (.25  milli- 
meter), width,  about  ioi^  (.1  millimeter).  Body  thin,  show- 
ing eyes,  vasiform  orifice,  and  caudal  setae  or  wax  tubes.  Ven- 
tral surface  shows  six  poorly  developed  legs :  eyes  and  antennae 
are  situated  near  anterior  end  of  body.  Mouthparts  are  in 
form  of  a  sucking  tube  having  its  origin  just  in  front  of  the  fore- 
legs. The  segmentation  is  apparent  in  the  abdominal  region. 
See  fig.  2.  1 

Full-grown  Nymph. — Length,  about  .75  millimeter.  Width, 
about  .5  millimeter  though  varying  considerably  in  size. 
Thickness,  about  .28  millimeter.  Greenish-white  in  color,  dor- 
sum  mildlv   convex   with   several    cross   sutures    indicative    of 


white-fly;  description.  9 

segmentation.  One  of  these  has  the  form  of  a  broad  and  shal- 
low caret  (  /\  )  not  far  from  the  middle  of  the  body.  A  median 
line  from  the  point  of  this  extends  to  the  anterior  end  of  the 
body,  and  it  is  along  this  line  and  across  through  the  caret- 
shaped  mark  that  the  skin  opens  for  the  adult  to  emerge.  A 
submarginal  row  of  short,  white,  wax  filaments  or  rods.  Under 
the  margin  and  extending  perpendicularly  from  the  horizontal 
plane  of  the  body  to  the  leaf  is  a  wall  of  wax  made  up  of  nar- 
row filaments  side  by  side  and  adjoining  each  other.  This  wax 
fastens  the  insect  to  the  leaf,  and  often  breaks  off  in  flakes  when 
the  nymph  is  removed  and  mounted  in  glycerine.  Even  when 
broken  off  this  wall  shows  the  parallel  lines  or  striae,  and  it  is 
along  these  that  it  separates  most  readily. 

In  the  fully  matured  nymph  or  so-called  pupa,  long  waxen 
rods  occur  on  the  dorsum  as  follows — a  pair  close  to  anterior 
margin  and  a  second  pair  a  short  distance  back  of  the  first.  A 
third  pair  on  the  thoracic  region.  The  fourth  and  fifth  pairs  are 
close  together  on  the  abdominal  region  just  back  of  the  caret- 
shaped  cross-mark.  The  sixth  pair  is  situated  near  the  vasi- 
form  orifice  and  a  seventh  pair  occurs  near  the  posterior  margin. 
These  rods  arise  from  distinct  pores  and  vary  greatly  in  length. 
The  mature  nymph  is  shown  in  figs.  3  and  4. 

~    \  i    , 


Fig.   3. — Mature  nymph  or  Fig.  4. — Lateral  view  of  mature 

pupa,  dorsal  view  :   X  36.  nymph  :    X  36. 

Adult  female. — Length,  about  1.5  millimeters  from  head  to 
ends  of  folded  wings.  Wing  expanse  of  about  2.5  millimeters. 
Body  plump  and  yellow  in  color,  terminating  in  an  ovipositor  of 
three  pieces.  Four  pure  white  wings  extending  beyond  end  of 
abdomen,  each  with  a  single  median  vein  which  in  the  fore  wings 
is  branched  at  the.  base ;  a  row  of  papillae  or  tubercles  resembling 


10         CONNECTICUT    EXPERIMENT    STATION,    BULLETIN    I40. 

beads  extends  around  the  margin,  and  each  papilla  bears  minute 
hairs.  These  are  shown  on  Plate  IV.  Eyes  brown,  in  two  pairs, 
the  upper  ones  slightly  smaller  than  the  lower,  but  with  a  larger 
number  of  facets.  Antennae  six-jointed,  the  first  joint  short  and 
thick,  the  second  long,  the  others  about  equal  in  length  and  all 
but  the  first  with  many  ring-like  markings.  Proboscis  of  three 
pieces  arising  from  under  the  back  side  of  the  head  and  contain- 
ing a  groove  in  which  are  four  bristle-like  lancets.  The  lancets 
have  a  different  origin  from  the  proboscis,  and  arise  from  the 
front  of  the  head.  Each  leg  has  two  tarsal  joints,  the  distal  one 
being  furnished  with  a  pair  of  claws  and  a  spine  or  bristle-like 
appendage.  Wings,  body  and  legs  covered  with  a  powdery 
white  wax.     See  fig.  5. 


Fig.   5. — Adult  female  :   X  36. 

Adult  male. — Like  female,  only  the  body  is  smaller  and  more 
pointed,  terminating  with  the  genital  organs.  Shown  on 
plate  II. 

Identity  and  Name  of  the  Insect. 
The  insect  was  first  noticed  at  the  Station  during  the  winter 
of  1894-95,  on  tomato  plants  under  glass.  During  1895,  the 
writer  sent  specimens  to  Prof.  M.  .V.  Slingerland  of  Cornell 
University,  and  later  to  Dr.  L.  O.  Howard  of  Washington,  both 
of  whom  reported  it  to  be  Aleyrodes,  but  that  it  was  impossible 
to  determine  the  species,  for  up  to  this  time  the  Aleyrodidcz  had 
received  but  little  study  in  this  country  and  few  American 
species  had  been  described.  Prof.  Garman,  to  whom  specimens 
were  sent,  pronounced  the  Connecticut  species  identical  with 
that  which  he  had  reported  as  attacking  strawberry  in  Kentucky. 


WHITE-FLY  ;    DESCRIPTION.  I  I 

During  the  past  year  the  writer  has  made  several  requests 
for  authoritatively  determined  specimens  from  England,  in 
order  to  settle  once  for  all  the  identity  of  the  insect.  Prof. 
David  Sharp  of  Cambridge  very  kindly  sent  some  adults  from 
the  botanical  garden  at  Cambridge,  which  presumably  were 
A.  vaporarioriim  Westw.,  but  as  Dr.  Sharp  makes  no  claim  to  a 
special  knowledge  of  the  group,  the  matter  is  still  unsettled. 
Moreover  the  pupa  case  is  needed  to  determine  the  species  with 
certainty.  The  adults  from  England  could  not  be  distinguished 
from  specimens  taken  in  the  Station  greenhouses. 

Garman  and  Packard,  in  the  works  of  these  authors  mentioned 
on  page  14,  write  of  this  insect  under  the  name  of  A.  vaporarium. 
Davis  uses  the  name  vaporarium  in  1894  (Insect  Life,  Vol.  VII, 
p.  174),  but  in  1896  (Special  Bull.  2,  Mich.  Exp.  Station)  adopts 
Westwood's  spelling.  The  difference  in  the  spelling  of  the 
specific  name  is  doubtless  due  to  an  oversight. 

For  the  generic  name  some  writers  use  the  Greek  spelling 
Alenrodes,  meaning  flour-like,  which  describes  the  waxy  or 
mealy  appearance  of  the  insects.  The  present  writer  has  pre- 
ferred the  original  spelling  as  given  by  Latreille  many  years 
ago. 

As  Westwood's  description  fits  our  species  very  well,  it  is 
probable  that  the  two  are  identical.  Westwood  described  and 
figured  the  species  in  the  Gardener's  Chronicle  for  1856,  p.  852. 
As  this  is  inaccessible  to  many,  the  description  is  here  repro- 
duced. 


Westwood's  Description  of  A.  vaporarioriim. 

The  Nezv  Aleyrodes  of  the  Greenhouse. — During  the  past  12 
months  the  greenhouses,  both  in  the  public  gardens  at  Kew  and 
in  the  gardens  of  the  Horticultural  Society  at  Chiswick,  have 
been  infested  with  a  new  pest,  under  the  appearance  of  a  very 
minute  white  four-winged  insect,  like  a  miniature  moth,  to  which 
my  attention  was  first  directed  by  Sir  William  Hooker,  and  sub- 
sequently by  Dr.  Lindley.  It  especially  attacks  the  leaves  of 
Mexican  species  of  Gonolobus,  Tecoma  velutina,  Bignonice, 
Aphelandrce,  Solanums,  and  other  similar  soft-leaved  plants,  and 
is  supposed  to  have  been  imported  with  living  plants  or  in  the 
packings  of   Orchidacece  from  Mexico,  in  all  cases  attaching 


12         CONNECTICUT    EXPERIMENT   STATION,    BULLETIN    I40. 

itself  to  the  under  side  of  the  leaf.  Here  it  sits  tranquilly  with 
the  tip  of  its  short  naked  sucker  or  rostrum  thrust  into  the  leaf, 
but  on  passing  the  hand  over  the  plants,  quite  a  little  white 
cloud  of  the  insects  is  raised.  They  soon,  however,  settle  again 
to  renew  their  attacks,  which  are  shortly  followed  by  a  dis- 
coloration and  blackening,  and  subsequent  drooping  and  falling 
of  the  leaves.  The  ordinary  fumigations  have  been  tried,  and 
the  winged  insects,  which  are  very  delicate  little  creatures,  are 
easily  killed,  but  in  a  day  or  two  a  fresh  brood  of  the  perfect 
insects  makes  its  appearance  in  as  great  numbers  as  before,  and 
this  continues  to  be  the  case  after  repeated  fumigations.  Nor  is 
the  placing  of  the  plants  out  in  the  open  air  more  successful  in 
getting  rid  of  the  enemy,  as  Mr.  Gordon  pointed  out  to  me  a 
cluster  of  plants  which  had  been  in  the  open  air  for  more  than  a 
fortnight,  and  which  were  swarming  with  the  insects  as  thickly 
as  those  within  doors. 

The  insect  when  seated  with  its  four  wings  closed  over  its 
back  is  not  larger  than  the  head  of  a  good-sized  pin,  and  were 
it  not  for  its  beautiful  clear  white  colour  it  would  be  seen  with 
difficulty.  A  microscopical  examination  proves  it  to  belong  to 
the  genus  Aleyrodes  (one  of  those  aberrant  groups  allied  to 
Aphis  and  Coccus),  of  which  we  possess  in  this  country  several 
native  species,  one  (A.  Chelidonii)  found  upon  Chelidonium 
majus,  and  also  on  the  common  cabbage ;  another,  first  deter- 
mined by  Mr.  Haliday,  infests  the  common  Phillyrea. 

The  body  is  soft  and  rather  fleshy,  the  head  distinct,  with  a 
pair  of  antennae  consisting  of  only  six  joints,  the  first  large,  the 
second  long,  and  the  four  following  short  and  slender ;  the  eyes 
are  four  in  number,  each  being  small  and  round,  the  two  on 
each  side  placed  near  each  other ;  the  rostrum  short,  fleshy, 
apparently  two-jointed,  emitting  from  its  apex  a  fine-pointed 
(certainly  compound)  black  seta,  which  is  the  real  instrument 
by  which  the  plants  are  wounded.  The  whole  body,  legs,  and 
wings  of  the  insect  are  covered  with  a  white  powdery  secretion, 
analogous  to  the  white  floccose  matter  of  the  Apple-blight 
Aphis,  the  white  mass  in  which  the  eggs  of  various  species  of 
Coccus  are  enveloped,  and  which  is  developed  in  many  other 
Homopterous  insects ;  the  wings  are  of  moderate  size,  rounded 
at  the  tips,  with  a  single  central  strong  rib ;  when  at  rest  they 
are  placed  over  the  back  roof-wise,  and  the  legs  are  rather  short 
and  simple. 


white-fly;   description.  13 

On  examining  some  of  the  infested  leaves  I  found  them 
covered  with  great  numbers  of  flat  bodies  of  extremely  delicate 
texture,  fringed  with  long,  straight,  slender  hairs  (having  a 
good  deal  of  the  appearance  of  some  small  species  of  mites)  ; 
their  number  was  greatest  on  the  lower  leaves  of  the  plants, 
and  I  counted  not  fewer  than  250  upon  a  single  leaf  of  moderate 
size.  They  are  of  an  oval,  flattened  form,  the  margin  being  very 
thin ;  the  fore  half  of  the  body  is  occupied  by  two  portions, 
which  shut  close  by  a  straight  slit  along  the  middle  of  the  back, 
but  are  generally  seen  more  or  less  opened  like  the  doors  of  a 
cupboard.  These  bodies  are  the  envelopes  of  the  pupae  of  the 
Aleyrodes,  which  have  already  made  their  escape  in  the  winged 
state,  but  with  them  were  mixed  many  much  smaller  specimens 
of  the  insect  destitute  of  the  fine  hairs  and  very  transparent,  of 
a  very  flat,  oval  figure,  the  middle  and  hinder  half  of  the  body 
exhibiting  traces  of  the  abdominal  segments,  with  the  anal 
apparatus  placed  at  some  distance  from  the  hinder  extremity  of 
the  body ;  the  rostrum,  very  minute  and  conical,  is  seen  at  some 
distance  from  the  anterior  extremity,  and  around  are  seen 
several  pairs  of  tubercles,  which  seem  to  represent  the  eyes, 
antennae,  and  legs,  and  which  are  seen  much  more  clearly  in 
Professor  Burmeister's  figures  of  the  young  of  Aleyrodes 
Chelidonii. 

The  present  species,  although  very  closely  resembling  A. 
Chelidonii,  differs  from  it  in  its  smaller  size,  in  having  only 
6- jointed  antennae,  in  the  want  of  the  dusky  spot  on  each  wing, 
in  the  more  suddenly  angled  rib  in  the  middle  of  the  fore- 
wings,  and  especially  in  the  long  straight  rigid  hairs  with  which 
the  body  of  the  pupa  case  is  defended,  and  within  which  the 
insect  lies  concealed  for  several  days,  unaffected  by  external 
agents  (except  heat  and  cold),  which  circumstance  explains  the 
cause  of  the  sudden  reappearance  of  the  insect  so  soon  after 
fumigation.  In  consequence  of  its  being  only  hitherto  known 
in  greenhouses  it  may  be  specifically  named  Aleyrodes  vapora- 

riorum 

J.  O.  West  wood. 


14      connecticut  experiment  station,  bulletin  i40. 

Bibliography. 

1856.  Westwood.  Gardeners'  Chronicle,  p.  852.  Original  description 
and  illustrations. 

1868.     Signoret.     Ann.  de  la  Soc.  Ent.  de  France,  p.  387.     Description. 

1871.  Packard.  American  Naturalist,  Vol.  4,  p.  686.  Illustrated. 
Brief  mention  as  attacking  strawberry  and  tomato. 

1880.  Riley.  Amer.  Ent.  (Vol.  3),  n.  s.,  Vol.  I.,  p.  129.  A  brief 
account  of  Aleyrodes  on  Oxalis. 

1889.  Packard.  Guide  to  the  Study  of  Insects,  9th  ed.,  p.  526.  Brief 
account,  p.  712.  Fig.  on  Plate  XIV.  Found  on  Strawberry  at  Amherst, 
Mass. 

1891.  Bailey.  Cornell  Exp.  Station,  Bull.  28,  p.  58.  Brief  mention  as 
attacking  tomatoes  in  greenhouse. 

1890.  Riley.     Insect  Life,  Vol.  II.,  p.  339.     Mentioned. 

1891.  Riley.  Insect  Life,  Vol.  III.,  p.  394.  Troublesome  in  green- 
houses, England. 

1891.  Garman.  Agr.  Science,  Vol.  V.,  p.  264.  Brief  description.  Same 
account  in  An.  Rep.,  Kent.  Exp.  Sta.,  1890.,  p.  37-38.  Numerous  on 
Strawberry  at  Lexington,  Kent. 

1892.  Riley.  Insect  Life,  Vol.  V.,  17.  Found  on  Strawberry  in  Dist. 
of  Columbia. 

1893.  Webster.  Rep.  Ohio  Exp.  Sta.,  p.  xxxv.  Very  abundant  on 
Strawberry,  but  no  serious  injury  resulted. 

1894.  Davis.  Insect  Life,  Vol.  VII.,  p.  174.  Brief  description.  Trou- 
blesome in  greenhouses  in  Michigan. 

1895.  Britton.  Conn.  Exp.  Sta.  Rep.,  p.  203.  Brief  description  and 
illustrations. 

1896.  Davis.  Mich.  Exp.  Sta.,  Miscellaneous  Bull.,*  p.  22.  Descrip- 
tion and  illustrations. 

1897.  Britton.  Garden  and  Forest,  Vol.  X.,  p.  194.  Brief  account. 
Illustrated. 

1900.  Britton.  Conn.  Exp.  Sta.  Rep.,  p.  311.  Fumigating  with  hydro- 
cyanic acid  gas. 

1900.  Quaintance.  U.  S.  Div.  of  Ent.,  Tech.  series  No.  8,  pp.  16  and 
39.     Distribution  and  key  to  the  species. 

1901.  Slingerland.  Cornell  Exp.  Sta.,  Bull.  190,  p.  155.  Attacking 
strawberries  in  New  York.     Illustrations  from  Davis. 

*  This  was  issued  as  Special  Bull.  2,  and  bears  the  date  of  November, 
1896.  Later  it  was  found  that  the  bulletin  numbers  had  been  duplicated 
and  this  was  chansred  to  Miscellaneous  Bulletin. 


white-fly;  remedies.  15 


Remedies. 


Fumigating. — Fumigating-  with  tobacco  is  the  remedy  that 
has  been  oftenest  recommended  for  this  insect,  but  the  fumes 
from  the  burning  of  ordinary  stems  or  dust  do  not  kill  any 
considerable  number  of  the  insects.  Many  are  stupefied  by  the 
fumes  and  fall  from  the  plants,  but  revive  later  and  soon  become 
as  active  as  ever.  During  the  past  two  or  three  years  tobacco 
used  in  this  way  seems  to  have  been  less  effective  in  destroying 
the  adults  than  when  the  writer  first  employed  it  eight  years 
ago.  Where' the  adults  are  stupefied  and  fall  to  the  ground,  a 
copious  watering  of  the  surface  of  the  soil  will  kill  them  in 
great  numbers. 

Fumigating  with  hydrocyanic  acid  gas  to  kill  the  white-fly 
was  here  first  given  a  trial  in  1900  and  an  account  of  the  experi- 
ment was  published  in  the  Report  of  this  Station  for  1900,  page 
311.  Three  ounces  of  potassium  cyanide  for  each  one  thousand 
cubic  feet  of  space  were  used,  and  the  house  closed  for  thirty 
minutes.  All  insects  were  killed,  but  the  tomato  plants  were 
more  or  less  injured.  Our  experiments  as  well  as  those  of 
others  indicate  that  the  tomato  is  more  susceptible  to  the  effects 
of  the  gas  than  most  plants,  and  care  must  therefore  be  taken  in 
fumigating  tomato  houses.  Several  trials  were  then  made  with 
two  and  one-half  ounces  for  each  thousand  cubic  feet  of  space 
and  the  results  were  similar.  Some  of  the  tomato  plants  were 
injured,  but  the  insects  were  killed  in  all  cases.  One  house 
which  was  old  and  not  very  tight  allowed  some  of  the  fumes  to 
escape,  so  that  the  plants  were  uninjured  though  the  insects  were 
all  killed. 

Dr.  J.  Fisher  used  one  ounce  of  cyanide  for  each  one  thousand 
cubic  feet  of  space  and  killed  all  the  insects  without  injury  to 
the  tomato  plants.* 

Spraying. — In  1895,  the  writer  used  whale-oil  soap  solution 
(1  lb.  of  soap  to  5  gallons  of  water)  in  the  form  of  a  spray  on 
the  under  surface  of  the  leaves  to  kill  the  nymphs.  The  result 
was  successful,  but  on  account  of  the  disagreeable  odor  of 
whale-oil  soap,  it  was  discarded.  Fir-tree  oil  (one-half  pint  in 
two  gallons  of  water)  gave  excellent  results  when  the  plants 
were  thoroughly  sprayed  with  the  solution.     The  adults  and 

*  Johnson,  Fumigation  Methods,  p.  136. 


1 6         CONNECTICUT    EXPERIMENT    STATION,    BULLETIN    I40. 

nymphs  which  were  moistened  by  the  spray  were  killed.  The 
cost  of  the  material,  however,  makes  the  treatment  an  expensive 
one  and  precludes  its  use  on  a  large  scale.  Fir-tree  oil  has  a 
pleasant  odor  and  is  not  objectionable  to  use  in  a  greenhouse 
of  ornamental  plants  or  even  in  a  dwelling. 

A  fine  spray  of  kerosene  and  water  (15  per  cent,  kerosene) 
was  then  applied  to  the  tomato  plants  on  sunny  days,  by  means 
of  a  "kerowater"  pump,  with  good  results  in  killing  the  insects. 

But  kerosene,  like  whale-oil  soap,  has  an  unpleasant  odor, 
and  occasionally  causes  a  slight  injury  to  the  foliage.  Even 
when  not  at  first  apparent,  the  leaves  in  some  instances  took  on 
later  a  brown  or  reddish  color  not  indicative  of  health,  and  some 
of  these  finally  dropped. 

Early  in  1901,  we  began  spraying  the  tomato  plants  with 
common  soap  and  water,  dissolving  one  pound  of  soap  in  eight 
gallons  of  water.  This  seemed  to  be  the  best,  all  things  con- 
sidered, of  any  of  the  sprays.  Not  only  was  it  effectual  in  kill- 
ing all  adults  and  nymphs  with  which  it  came  in  contact,  but  it 
was  both  inexpensive  and  inodorous,  and  at  first  did  not  appear 
to  cause  the  slightest  injury  to  the  plants.  The  soap  was  cut 
in  thin  slices,  then  dissolved  in  hot  water,  and  cold  water  added 
to  make  the  right  proportions.  The  plants  received  one  applica- 
tion each  week  for  about  three  months,  when  some  of  the  leaves 
finally  exhibited  signs  of  injury. 

As  the  plants  had  never  been  sprinkled  with  water  from  the 
hose,  and  had  received  frequent  applications  of  soap,  the  leaves 
finally  became  coated  over  with  soap  to  such  an  extent  as  to 
seriously  interfere  with  the  normal  processes  of  respiration. 
The  lower  leaves  in  some  cases  shriveled  and  dropped.  A  few 
sprayings  cause  no  injury,  and  probably  none  would  be  done  in 
any  case  if  the  plants  are  sprinkled  freely  with  water  to  remove 
the  excess  of  soap. 

The  chief  difficulty  with  sprays  of  any  kind  is  that  it  is 
impossible  to  reach  all  places  where  the  insects  are  located. 
Many  leaves  are  curled  so  that  the  spray  cannot  reach  the  under 
side,  and  there  are  always  portions  of  plants  which  do  not,  on 
account  of  location  perhaps,  receive  a  thorough  treatment ;  this 
permits  the  escape  of  a  sufficient  number  of  adults,  or  of 
nymphs  which  soon  change  to  adults,  to  keep  the  house  infected. 


white-fly;   summary.  ij 

Summary. 

1.  The  white-fly  has  been  the  worst  insect  pest  of  tomatoes 
and  cucumbers  under  glass  at  the  Station  during  the  past  eight 
years.  Many  florists'  plants  are  also  injured,  and  the  insect  has 
attacked  strawberry  and  many  other  plants  out  of  doors  in 
summer.  It  has  been  received  from  several  growers  in  Con- 
necticut, and  is  widely  distributed  over  the  northeastern  United 
States.     Its  original  home  is  unknown. 

2.  The  white-fly  is  closely  related  to  the  scale-insects,  and  to 
the  plant  lice.  It  resembles  the  former  in  its  immature  stages, 
but  differs  from  it  in  that  both  sexes  are  winged  when  reaching 
the  adult  stage. 

3.  It  injures  plants  by  sucking  the  sap,  from  the  under  sides 
of  the  leaves.  The  lower  leaves  are  the  first  to  shrivel  and 
drop.  Most  of  the  injury  is  caused  by  the  nymphs  or  imma- 
ture insects. 

4.  The  nymphs  of  the  white-fly  have  been  found  upon  fifty- 
eight  different  kinds  of  plants  in  Connecticut. 

5.  About  five  weeks  are  required  for  the  white-fly  to  pass 
through  its  life-stages,  all  of  which  are  found  on  the  under  sides 
of  the  leaves.  Eggs  hatch  in  eleven  days,  and  the  young 
nymphs  crawl  for  a  short  time,  when  they  become  stationary  and 
secrete  wax  in  long  filaments.  When  the  adults  emerge,  the 
pupa  skins  remain  attached  to  the  leaves.  It  is  not  yet  known 
whether  the  species  can  survive  the  winter  unprotected  in  this 
climate,  but  it  is  carried  over  on  plants  in  greenhouses  and 
dwellings. 

6.  It  is  thought  to  be  identical  with  the  European  species 
A.  vaporariorum  of  Westwood,  but  this  has  not  yet  been  fully 
determined. 

7.  Fumigating  with  tobacco  is  not  an  effective  remedy. 
Hydrocyanic  acid  gas  (using  two  and  one-half  ounces  of  potas: 
shim  cyanide  for  each  one  thousand  cubic  feet)  killed  the 
insects  but  injured  tomato  plants.  Dr.  Fisher  used  one  ounce 
of  cyanide  and  did  not  injure  his  plants,  but  killed  all  of  the 
insects. 

8.  Spraying  the  under  surfaces  of  the  leaves  with  common 
laundry  soap  and  water  (one  pound  dissolved  in  eight  gallons) 
proved  to  be  a  cheap  and  effective  remedy.  If  applied  fre- 
quently, however,  the  soap  should  be  occasionally  washed  from 
the  leaves  by  spraying  them  with  clear  water. 


PLATE  I. 


a.     Nymphs  :  Enlarged  about  four  times. 


«■  ■  •  ,t  '-. 


;*#^m^ 


b.     Adults  and  pupa  skins.     Enlarged  four  times. 
THE    WHITE-FLY   ON    TOBACCO    LEAF. 


PLATE  II. 


a.     Female  and  male  :  much  enlarged. 


c.     Antenna,   showing  ring-like 
markings  :  much  enlarged. 


b.     Nymphs  and  adults  ;  twice  natural  size. 

THE   WHITE-FLY. 


PLATE  III. 


a.     Egg,  showing  stalk  :  much  enlarged. 


b.    Adult  female,  ventral  view,  showing  pro- 
boscis :  much  enlarged. 


c.     Genital  organs  of  male  :  much  d.     Ovipositor  of  female  :  much  enlarged, 

enlarged. 


THE    WHITE-FLY. 


PLATE  IV. 


a.     Edge  of  wing  :  much  enlarged. 


c.     Foot :  greatly  enlarged. 


b.     Fore  wing  :  greatly  enlarged. 

THE    WHITE-FLY. 


University  of 
Connecticut 

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